The C-Max was previously rated at 47/47/47 (city/highway/combined), but the company announced today that it would lower those numbers to 45/40/43 (city/highway/combined). The biggest hit came on the highway, where the C-Max saw its rating drop by seven miles per gallon. The new combined rating puts the C-Max just one mile per gallon higher than its chief rival: the Toyota Prius v.

In addition, customer that bought a C-Max will receive a $550 cash rebate from Ford; lessees will receive $325.

2013 Ford C-Max Hybrid

“Ford is absolutely committed to being a leader in the hybrid market and to top fuel efficiency across our lineup,” said Raj Nair, group vice president, global product development. “We are taking actions with our popular C-MAX Hybrid so that customers are even more satisfied with the vehicle’s on-road fuel efficiency performance.”

In its testing, Consumer Reports indicated that the C-Max was only good for 35/38/37 (city/highway/combined). In response to Consumer Reports' story, Ford spokesman Wes Sherwood said in April, "Early C-Max Hybrid and Fusion Hybrid customers praise the vehicles and report a range of fuel economy figures, including some reports above 47 mpg. This reinforces the fact that driving styles, driving conditions and other factors can cause mileage to vary."

For their part, C-Max drivers over at Fuelly reported an average of 40.2 mpg combined -- still nearly three miles per gallon below Ford's new combined rating.

C-Max drivers on Fuelly.com showed just how optimistic the original ratings were

"This is an industrywide issue with hybrid vehicles," explained Nair. "We've learned along with EPA that the regulations create some anomalies for hybrid vehicles under the general label rule."

The EPA has explained [PDF] the reason why the C-Max was previously rated for 47 mpg across the board, and why the new numbers are lower. It appears that Ford used a provision in the EPA testing to allow it to use the fuel economy numbers from the Fusion Hybrid on the C-Max because they used the same powertrain and weighed the same. However, the Fusion is a more aerodynamic vehicle, hence the huge discrepancy in the real world on the C-Max:

Ford based the 2013 Ford C-Max label on testing of the related Ford Fusion hybrid, which has the same engine, transmission and test weight as allowed under EPA regulations. For the vast majority of vehicles this approach would have yielded an appropriate label value for the car, but these new vehicles are more sensitive to small design differences than conventional vehicles because advanced highly efficient vehicles use so little fuel.

In this case, EPA’s evaluation found that the C-Max’s aerodynamic characteristics resulted in a significant difference in fuel economy from the Fusion hybrid.